Abstract:We examined the NaCl resistant potential of four energy willow clones (Salix. dasyclados, S. ‘Mesu Neko’, S. fragilis, S. viminalis) and one wild clone (S. matsudana) grown on containers with five soil NaCl concentrations (0, 02%, 0.4%, 0.6% and 0.8%). After 45 days′ salt stress, gas exchange, protective enzyme activities and the organic substance for osmotic adjustment were measured. We found that (1) the decline of photosynthetic rate of four energy clones was caused by stomata factors when soil NaCl concentration < 0.4%, while it was mainly caused by non-stomata factors when soil NaCl concentration > 0.4%. (2) With NaCl increasing, the CAT activities of four energy clones decreased consistently; POD activities increased at the lower concentrations and then decreased at the higher concentrations; SOD activities consistently increased. The activity of the protective enzymes of four energy clones was higher than that of S. matsudana under the salt stress. (3) When soil NaCl concentration was lower than 0.6%, the soluble protein content of four energy clones were all higher than S. matsudana, S. fragilis′s proline content was higher than S. matsudana in the whole process of the salt stress. (4) All seedlings from four energy clones grew well in the soil with 0.4% NaCl concentration compared with S. matsudana. S. fragilis showed a better endurance under the salt stress and grew well in the soil of 0.6% NaCl concentration. These results indicate that four energy clones can grow well on light and moderate salt soils in Tianjin.